This is a pretty standard example of the kind of 1950's sci-fi movie that, on the one hand, now comes across as thoroughly dated and often unintentionally funny, but that also has a certain charm, at least to those who can appreciate the genre. This is not a bad film of its kind, despite its deficiencies.
The "Crash of Moons" has to do with a pair of 'gypsy moons', one of which is inhabited, that are locked into an irregular orbit around each other (as one character helpfully describes it, 'like two children on a playground'), and that are headed for a collision with another inhabited moon. The 'United Worlds' sends Space Ranger Rocky Jones and his friends to save everybody. One of the moons (whose leader is John Banner, better known as Sergeant Schultz from "Hogan's Heroes") is quite cooperative, but the other world is ruled by an entertainingly mean-spirited queen who, for reasons that apparently satisfy her, would rather eliminate the Space Rangers than have their help.
Most of the characters are stereotypes, but the actors are not bad, and most of them seem to enjoy what they are doing, which gives it some real life most of the time. Some of the events and much of the jargon in the dialogue lack any plausibility, but the basic premise of the impending collision comes across pretty well, and creates some real interest. The direction could have been a lot better, because in many of the crises the tension is prematurely defused, but on the other hand there is usually enough going on to keep the viewer's interest. The 'special' effects are about what you would expect, but at least they're good for some chuckles.
This movie won't be of general interest today, but if you enjoy movies such as "Plan 9 From Outer Space", this one is worth a look. "Crash of Moons" is not nearly as uproariously inept (what movie is), but it will keep your attention and provide some light entertainment.